Information architecture is an integral component when it comes to ensuring optimum maintenance and performance of a portal. Good planning is a prerequisite to building an optimal structure.
After creating a SharePoint site, permission levels come into picture. A user may want to provide or restrict access to a site or its contents. Other than the conventional groups and permissions levels provided, a user can even devise permissions way beyond the default levels.
Understanding permissions inheritance
If a user works on a site, he/she is essentially working inside a site collection. In a nutshell, every site exists in site collection i.e. there is a group of sites under a single top-level site. The top-level site is called the root site of the site collection.
Shown below is an illustration of a site collection depicting a simple hierarchy of sites, lists and list items.